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1.
Chemosphere ; 239: 124803, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31520973

RESUMO

Nitrogen biogeochemistry occupies a central role in nitrogen cycles and exerts a significant influence on primary productivity and global carbon cycles. In order to better understand the nitrogen biogeochemistry in coastal regions, spatiotemporal nitrogen fixation, denitrification and anammox were investigated in the coastal regions of northern Beibu Gulf (NBG), South China Sea (SCS). Nitrogen fixation was mainly detected in the water column of outer bays, attributed to the low nitrate concentration and low N/P (N/P < 16). Comparisons of the nitrogen fixation rates between unicellular (<10 mm) and the filamentous diazotrophs (>10 mm) indicated that the contribution of unicellular diazotrophs was more important than filamentous diazotrophs. Besides, field investigation revealed that Richelia was the dominant species in filamentous diazotrophs. On the other hand, both denitrification and anammox were found in the surface sediment and denitrification dominated the nitrogen loss process. Denitrification was mainly related to the nitrate concentration in pore water and organic matter in the sediment, while anammox was mainly regulated by the concentration of nitrate and nitrite in pore water. Additionally, temperature, dissolved oxygen (DO) and salinity also had an impact on denitrification and anammox. The net areal yield of nitrogen biogeochemical processes was estimated to be -1079t/a, as an important pathway of nitrogen removal. This study adds to the knowledge of nitrogen biogeochemistry in the nutrient-replete coastal region and highlights its significance in such an environment.


Assuntos
Baías/química , Ciclo do Nitrogênio , Nitrogênio/química , Baías/microbiologia , Ciclo do Carbono , China , Cianobactérias/metabolismo , Desnitrificação , Nitratos/química , Nitritos/química , Nitrogênio/análise , Fixação de Nitrogênio , Oxigênio/química , Salinidade , Análise Espaço-Temporal
2.
Chemosphere ; 240: 124966, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31726608

RESUMO

The hepatotoxic cyanotoxins microcystins (MCs) are emerging contaminants naturally produced by cyanobacteria. Yet their ecological role remains unsolved, previous research suggests that MCs have allelopathic effects on competing photosynthetic microorganisms, even eliciting toxic effects on other freshwater cyanobacteria. In this context, the bioluminescent recombinant cyanobacterium Anabaena sp. PCC7120 CPB4337 (hereinafter Anabaena) was exposed to extracts of MCs. These were obtained from eight natural samples from freshwater reservoirs that contained MCs with a concentration range of 0.04-11.9 µg MCs L-1. MCs extracts included the three most common MCs variants (MC-LR, MC-RR, MC-YR) in different proportions (MC-LR: 100-0%; MC-RR: 100-0%; MC-YR: 14.2-0%). The Anabaena bioassay based on bioluminescence inhibition has been successfully used to test the toxicity of many emerging contaminants (e.g., pharmaceuticals) but never for cyanotoxins prior to this study. Exposure of Anabaena to MCs extracts induced a decrease in its bioluminescence with effective concentration decreasing bioluminescence by 50% ranging from 0.4 to 50.5 µg MC L-1 in the different samples. Bioluminescence responses suggested an interaction between MCs variants which was analyzed via the Additive Index method (AI), indicating an antagonistic effect (AI < 0) of MC-LR and MC-RR present in the samples. Additionally, MC extracts exposure triggered an increase of intracellular free Ca2+ in Anabaena. In short, this study supports the use of the Anabaena bioassay as a sensitive tool to assess the presence of MCs at environmentally relevant concentrations and opens interesting avenues regarding the interactions between MCs variants and the possible implication of Ca2+ in the mode of action of MCs towards cyanobacteria.


Assuntos
Bioensaio/métodos , Ecotoxicologia/métodos , Microcistinas/toxicidade , Anabaena/efeitos dos fármacos , Anabaena/metabolismo , Cálcio/metabolismo , Cianobactérias/isolamento & purificação , Cianobactérias/metabolismo , Água Doce/microbiologia
3.
Chemosphere ; 240: 124880, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31542581

RESUMO

Microginins (MGs) are bioactive metabolites mainly produced by Microcystis spp., (Cyanobacteria) commonly found in eutrophic environments. In this study, the cytotoxic and genotoxic activities of four MG congeners (MG FR3, MG GH787, cyanostatin B, MGL 402) and a well characterized cyanobacterial extract B-14-01 containing these metabolites were evaluated in the human hepatocellular carcinoma (HepG2) cell line. The cytotoxicity was measured with the MTT assay, while genotoxicity was studied with the comet, γH2AX and cytokinesis block (CBMN) micronucleus assays. The viability of cells after 24 h was significantly affected only by the extract, whereas after 72 h a concentration dependent decrease in cell proliferation was observed for the extract and tested microginins, with MGL 402 being the most potent and MG FR3 the least potent congener. The extract and all tested congeners induced DNA strand breaks after 4 and 24 h exposure. The most potent was the extract, which induced concentration and time dependent increase in DNA damage at concentrations ≥0.01 µg mL-1. Among microginins the most potent was MGL 402 (increase in DNA strand breaks at ≥ 0.01 µg mL-1) and MG FR3 was the least potent (increase in DNA strand breaks at ≥ 1 µg mL-1). However, no induction of DNA double strand breaks was observed after 24 and 72-h exposure to the cyanobacterial extract or MGs. Induction of genomic instability was observed in cells exposed to MG GH787, cyanostatin B and the extract B-14-01. This study is the first to provide the evidence that microginins exert genotoxic activity.


Assuntos
Carcinoma Hepatocelular/patologia , Cianobactérias/metabolismo , Dano ao DNA/genética , Instabilidade Genômica , Neoplasias Hepáticas/patologia , Oligopeptídeos/farmacologia , Carcinoma Hepatocelular/genética , Ensaio Cometa , Dano ao DNA/efeitos dos fármacos , Células Hep G2 , Humanos , Neoplasias Hepáticas/genética , Testes para Micronúcleos
4.
Environ Sci Pollut Res Int ; 26(34): 35107-35120, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31679142

RESUMO

In freshwater ecosystem, phototrophic biofilms play a crucial role through adsorption and sequestration of organic and inorganic pollutants. However, extracellular polymeric substance (EPS) secretion by phototrophic biofilms exposed to metals is poorly documented. This work evaluated the physiological responses of phototrophic biofilms by exposing three microorganisms (cyanobacterium Phormidium autumnale, diatom Nitzschia palea and green alga Uronema confervicolum) to 20 and 200 µg L-1 of Cu or 60 and 600 µg L-1 of Zn, both individually and in combination. Analysis of metal effects on algal biomass and photosynthetic efficiency showed that metals were toxic at higher concentrations for these two parameters together and that all the strains were more sensitive to Cu than to Zn. U. confervicolum was the most impacted in terms of growth, while P. autumnale was the most impacted in terms of photosynthetic efficiency. In consequence to metal exposure at higher concentrations (Cu200, Zn600 and Cu200Zn600), a higher EPS production was measured in diatom and cyanobacterium biofilms, essentially caused by an overproduction of protein-like polymers. On the other hand, the amount of secreted polysaccharides decreased during metal exposure of the diatom and green alga biofilms. Size exclusion chromatography revealed specific EPS molecular fingerprints in P. autumnale and N. palea biofilms that have secreted different protein-like polymers during their development in the presence of Zn600. These proteins were not detected in the presence of Cu200 despite an increase of proteins in the EPS extracts compared to the control. These results highlight interesting divergent responses between the three mono-species biofilms and suggest that increasing protein production in EPS biofilms may be a fingerprint of natural biofilm against metal pollutants in freshwater rivers.


Assuntos
Biofilmes/crescimento & desenvolvimento , Cobre/toxicidade , Zinco/toxicidade , Biofilmes/efeitos dos fármacos , Biomassa , Cobre/análise , Cianobactérias/metabolismo , Diatomáceas/metabolismo , Ecossistema , Matriz Extracelular de Substâncias Poliméricas , Água Doce , Metais/análise , Fotossíntese , Rios , Zinco/análise
5.
J Photochem Photobiol B ; 201: 111684, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31733505

RESUMO

Since the beginning of life on Earth, cyanobacteria have been exposed to natural ultraviolet-A radiation (UV-A, 315-400 nm) and ultraviolet-B radiation (UV-B, 280-315 nm), affecting their cells' biomolecules. These photoautotrophic organisms have needed to evolve to survive and thus, have developed different mechanisms against ultraviolet radiation. These mechanisms include UVR avoidance, DNA repair, and cell protection by producing photoprotective compounds like Scytonemin, carotenoids, and Mycosporine-like amino acids (MAAs). Lyngbya marine species are commercially important due to their secondary metabolites that show a range of biological activities including antibacterial, insecticidal, anticancer, antifungal, and enzyme inhibitor. The main topic in this review covers the Lyngbya sp., a cyanobacteria genus that presents photoprotection provided by the UV-absorbing/screening compounds such as MAAs and Scytonemin. These compounds have considerable potentialities to be used in the cosmeceutical, pharmaceutical, biotechnological and biomedical sectors and other related manufacturing industries with an additional value of environment friendly in nature. Scytonemin has UV protectant, anti-inflammatory, anti-proliferative, and antioxidant activity. MAAs act as sunscreens, provide additional protection as antioxidants, can be used as UV protectors, activators of cell proliferation, skin-care products, and even as photo-stabilizing additives in paints, plastics, and varnishes. The five MAAs identified so far in Lyngbya sp. are Asterina-330, M-312, Palythine, Porphyra-334, and Shinorine are capable of dissipating absorbed radiation as harmless heat without producing reactive oxygen species.


Assuntos
Aminoácidos/química , Cianobactérias/metabolismo , Cicloexanóis/química , Indóis/química , Fenóis/química , Protetores Solares/química , Raios Ultravioleta , Aminoácidos/isolamento & purificação , Antioxidantes/química , Cicloexanóis/isolamento & purificação , Indóis/isolamento & purificação , Fenóis/isolamento & purificação , Protetores Solares/metabolismo
6.
Biochim Biophys Acta Bioenerg ; 1860(11): 148084, 2019 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-31520614

RESUMO

Photosynthetic [2Fe-2S] plant-type ferredoxins have a central role in electron transfer between the photosynthetic chain and various metabolic pathways. Several genes are coding for [2Fe2S] ferredoxins in cyanobacteria, with four in the thermophilic cyanobacterium Thermosynechococcus elongatus. The structure and functional properties of the major ferredoxin Fd1 are well known but data on the other ferredoxins are scarce. We report the structural and functional properties of a novel minor type ferredoxin, Fd2 of T. elongatus, homologous to Fed4 from Synechocystis sp. PCC 6803. Remarkably, the midpoint potential of Fd2, Em = -440 mV, is lower than that of Fd1, Em = -372 mV. However, while Fd2 can efficiently react with photosystem I or nitrite reductase, time-resolved spectroscopy shows that Fd2 has a very low capacity to reduce ferredoxin-NADP+ oxidoreductase (FNR). These unique Fd2 properties are discussed in relation with its structure, solved at 1.38 Šresolution. The Fd2 structure significantly differs from other known ferredoxins structures in loop 2, N-terminal region, hydrogen bonding networks and surface charge distributions. UV-Vis, EPR, and Mid- and Far-IR data also show that the electronic properties of the [2Fe2S] cluster of Fd2 and its interaction with the protein differ from those of Fd1 both in the oxidized and reduced states. The structural analysis allows to propose that valine in the motif Cys53ValAsnCys56 of Fd2 and the specific orientation of Phe72, explain the electron transfer properties of Fd2. Strikingly, the nature of these residues correlates with different phylogenetic groups of cyanobacterial Fds. With its low redox potential and its discrimination against FNR, Fd2 exhibits a unique capacity to direct efficiently photosynthetic electrons to metabolic pathways not dependent on FNR.


Assuntos
Proteínas de Bactérias/metabolismo , Cianobactérias/metabolismo , Ferredoxinas/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Cianobactérias/genética , Ferredoxinas/química , Ferredoxinas/genética , Ligações de Hidrogênio , Cinética , Modelos Moleculares , Filogenia , Alinhamento de Sequência
7.
Aquat Toxicol ; 216: 105315, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561138

RESUMO

Blooms of cyanobacteria, a common event in eutrophic environments, result in the release of potentially toxic substances into the water. The cyanobacterium Radiocystis fernandoi produces microcystin (MC) and other peptides that may disturb homeostasis. This study evaluated the effect of intraperitoneal injections containing the crude extract (CE) of R. fernandoi strain R28 on the gills and kidneys of neotropical fish, Piaractus mesopotamicus, 3, 6 and 24 h post-injection. CE contained MC-RR, MC-YR and minor other oligopeptides. Plasma ions and the activities of the enzymes PP1 and PP2A, Na+/K+-ATPase (NKA), H+-ATPase (HA) and carbonic anhydrase (CA) were determined and morphological changes in both the gills and kidneys were characterized. Compared to controls, the concentration of Na+ within the plasma of P. mesopotamicus decreased after treatment with CE 3 h post treatment and increased after 24 h; the concentration of K+ decreased after 6 h. The activity of the endogenous PP1 and PP2A was unchanged in the gills and was inhibited in the kidneys 6 h after i.p. injection. In the gills, NKA activity increased after 3 h and decreased 6 h post i.p. exposure. Further, NKA activity did not differ from the controls 24-h post injection. In the kidneys, NKA, HA and CA activities were unaffected by treatment. The mitochondria-rich cell (MRC) density in the gills decreased after 3 h in the filament and 3 and 6 h in the lamellae and was restored to the control levels 24 h post-exposure. Filament epithelial hyperplasia and hypertrophy, lamellar atrophy and rupture of the lamellar epithelium were the most common effects of treatment in the gills. No histopathological changes occurred in the kidneys. This study demonstrates that a single dose of toxic CE from R. fernandoi can cause a transitory ion imbalance in P. mesopotamicus which is related to the changes in MRC levels and NKA activity. Ionic balance was recovered 24 h post i.p. injection, however, morphological changes that occurred in the gills took a longer amount of time to return to normal. To conclude, the effects of components contained within the CE of R. fernandoi may be harmful to P. mesopotamicus. In particular, the recovery of ionic regulation depends on MRC responses and histopathological changes produced by CE may affect gas exchange and other gill functions.


Assuntos
Caraciformes/fisiologia , Misturas Complexas/toxicidade , Cianobactérias/metabolismo , Exposição Ambiental , Osmorregulação , Animais , Caraciformes/sangue , Cloretos/sangue , Creatinina/sangue , Brânquias/efeitos dos fármacos , Brânquias/enzimologia , Brânquias/patologia , Íons/sangue , Rim/efeitos dos fármacos , Rim/enzimologia , Rim/patologia , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Osmorregulação/efeitos dos fármacos , Potássio/sangue , ATPases Translocadoras de Prótons/metabolismo , Sódio/sangue , ATPase Trocadora de Sódio-Potássio/metabolismo , Poluentes Químicos da Água/toxicidade
8.
Sensors (Basel) ; 19(16)2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31430858

RESUMO

Due to their ecological relevance, low cost, and easy maintenance, cyanobacteria have been used for bioreporter development. In this study, a battery of cyanobacterial bioreporters has been used to assess the ecotoxicity of four highly used metallic nanoparticles (NPs). The toxicity of these NPs was tested using the bioreporter Nostoc CPB4337 (Anabaena CPB4337). As oxidative stress is a primary toxic mechanism of metallic NPs, cyanobacterial reactive oxygen species (ROS)-detecting bioreporters were used. Metallic NPs release metal ions, which contribute to their toxic effect and the formation of ROS, so a metal-detecting bioreporter was also used to detect the bioavailable metals. The results confirm that ROS production by NPs was due to the NPs per se and not by released free-ions, which in fact were almost undetectable. Although the metal-detecting bioreporter could not detect the dissolved metal ions, it was able to detect the metallic NPs themselves, indicating that this bioreporter may be useful to detect them in the environment. ROS production varied depending on the growth medium or environmental matrices conditions and on the NP type. This work demonstrated the different levels of ROS production by metallic NPs and the importance of nanotoxicology studies in real matrices.


Assuntos
Cianobactérias/efeitos dos fármacos , Poluentes Ambientais/toxicidade , Medições Luminescentes/métodos , Nanopartículas Metálicas/toxicidade , Espécies Reativas de Oxigênio/análise , Cianobactérias/metabolismo , Poluentes Ambientais/química , Nanopartículas Metálicas/química , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Prata/química , Titânio/química
9.
Sci Total Environ ; 696: 133909, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31454606

RESUMO

Cyanobacteria blooms are increasing globally, with further increases predicted in association with climate change. Recently, some cyanobacteria species have been identified as a source of estrogenic effects in aquatic animals. To explore possible estrogenic effects of Microcystis aeruginosa (an often-dominant cyanobacteria species) on zooplankton, we examined effects of cyanobacteria exudates (MaE, 2 × 104 and 4 × 105 cells/ml) on reproduction in Daphnia magna. We analyzed physiological, biochemical and molecular characteristics of exposed Daphnia via both chronic and acute exposures. MaE at both low and high cell density enhanced egg number (15.4% and 23.3%, respectively) and reproduction (37.7% and 52.4%, respectively) in D. magna similar to 10 µg/L estradiol exposure. In addition, both MaE of low and high cell densities increased population growth rate (15.8% and 19.6%, respectively) and reproductive potential (60% and 83%, respectively) of D. magna. These exudates promoted D. magna reproduction by stimulating 17ß-hydroxysteroid-dehydrogenase (17ß-HSD) activity and production of ecdysone and juvenile hormone, and by enhancing vitellogenin biosynthesis via up-regulating expression of Vtg1 and Vtg2. However, increased expression (6.6 times higher than controls) of a detoxification gene (CYP360A8) indicated that MaE might also induce toxicity in D. magna. Reproductive interference of zooplankton by blooming cyanobacteria might negatively affect foodwebs because MaE-induced zooplankton population increase would enhance grazing and reduce abundance of edible algae, thereby adding to the list of known disruptive properties of cyanobacterial blooms.


Assuntos
Cladóceros/fisiologia , Cianobactérias/crescimento & desenvolvimento , Congêneres do Estradiol , Eutrofização , Animais , Cianobactérias/metabolismo , Daphnia , Estradiol , Estrogênios , Microcystis , Reprodução , Poluentes Químicos da Água/toxicidade , Zooplâncton
10.
Chemosphere ; 236: 124342, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31326752

RESUMO

The growth of algae in water and the taste and odour compounds produced by algal metabolism present a threat to water quality, public health and aquatic ecosystems and cannot be effectively removed by conventional water treatment processes. In this paper, a hydroxyl radical (OH)-based drinking water treatment system (DWTS) with a capacity of 480 m3 per day was built in the Xinglin water plant, Xiamen, China. With pretreatment at 0.88 mg L-1, sand filtration, and disinfection at 0.31 mg L-1 during the conveyance of algae-laden water within only 9.8 s, OH removed all five kinds of algae, with a total content of 35,180 cells mL-1, while ClO2 treatment left live and dead algae at 7150 cells mL-1, which would be transported into the pipe networks for the drinking water supply. Meanwhile, OH degraded 2-Methylisoborneol (2-MIB) from 175 to 4.4 ng L-1, which was below the Chinese standard of 10 ng L-1, while ClO2 degraded 2-MIB only to 155 ng L-1. Based on analyses of the mass spectra database, OH could mineralize 2-MIB by opening the ring structures of 2,2-dimethyl-1,3-cyclopentanedione and 2-methyl-cyclohexenecarboxaldehyde to produce small-molecule compounds. After OH pretreatment and OH disinfection, all water quality and disinfection by-product indexes met the Chinese Sanitary Standards for Drinking Water. Therefore, OH advanced oxidation produced using strong ionization discharge could be practically applied for the degradation of 2-MIB during the treatment of algae-laden water in the OH DWTS.


Assuntos
/química , Compostos Clorados/química , Cianobactérias/metabolismo , Radical Hidroxila/análise , Óxidos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , China , Diaminas/química , Desinfecção/métodos , Água Potável/química , Ecossistema , Filtração/métodos , Odorantes/análise , Oxirredução , Propano/análogos & derivados , Propano/química , Paladar , Qualidade da Água , Abastecimento de Água
11.
ScientificWorldJournal ; 2019: 1030236, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31346323

RESUMO

The unicellular halotolerant cyanobacterium Aphanothece halophytica is a potential dark fermentative producer of molecular hydrogen (H2) that produces very little H2 under illumination. One factor limiting the H2 photoproduction of this cyanobacterium is an inhibition of bidirectional hydrogenase activity by oxygen (O2) obtained from splitting water molecules via photosystem II activity. The present study aimed to investigate the effects of the photosystem II inhibitors carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) on H2 production of A. halophytica under light and dark conditions and on photosynthetic and respiratory activities. The results showed that A. halophytica treated with CCCP and DCMU produced H2 at three to five times the rate of untreated cells, when exposed to light. The highest H2 photoproduction rates, 2.26 ±â€Š0.24 and 3.63 ±â€Š0.26 µmol H2 g-1 dry weight h-1, were found in cells treated with 0.5 µM CCCP and 50 µM DCMU, respectively. Without inhibitor treatment, A. halophytica incubated in the dark showed a significant increase in H2 production compared with cells that were incubated in the light. Only CCCP treatment increased H2 production of A. halophytica during dark incubation, because CCCP functions as an uncoupling agent of oxidative phosphorylation. The highest dark fermentative H2 production rate of 39.50 ±â€Š2.13 µmol H2 g-1 dry weight h-1 was found in cells treated with 0.5 µM CCCP after 2 h of dark incubation. Under illumination, CCCP and DCMU inhibited chlorophyll fluorescence, resulting in a low level of O2, which promoted bidirectional hydrogenase activity in A. halophytica cells. In addition, only CCCP enhanced the respiration rate, further reducing the O2 level. In contrast, DCMU reduced the respiration rate in A. halophytica.


Assuntos
Carbonil Cianeto m-Clorofenil Hidrazona/farmacologia , Cianobactérias/efeitos dos fármacos , Cianobactérias/metabolismo , Diurona/farmacologia , Hidrogênio/metabolismo , Complexo de Proteína do Fotossistema II/antagonistas & inibidores , Respiração Celular/efeitos dos fármacos , Respiração Celular/efeitos da radiação , Clorofila A/metabolismo , Escuridão , Hidrogenase/metabolismo , Fotossíntese/efeitos dos fármacos
12.
Biochim Biophys Acta Bioenerg ; 1860(9): 689-698, 2019 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-31336103

RESUMO

The binding of FNR to PSI has been postulated long ago, however, a clear evidence is still missing. In this work, using isothermal titration calorimetry (ITC), we found that FNR binds to photosystem I with its light harvesting complex I (PSI-LHCI) from C. reinhardtii with a 1:1 stoichiometry, a Kd of ~0.8 µM and ∆H of -20.7 kcal/mol. Titrations at different temperatures were used to determine the heat capacity change, ∆CP, of the binding, through which the size of the interface area between the proteins was assessed as ~3000 Å2. In a different set of ITC experiments, introduction of various sucrose concentrations was used to estimate that ~95 water molecules are released to the solvent. These observations support the notion of a binding site shared by few of the photosystem I - light harvesting complex I (PSI-LHCI) subunits in addition to PsaE. Based on these results, a hypothetical model was built for the binding site of FNR at PSI, using known crystallographic structures of: cyanobacterial PSI in complex with ferredoxin (Fd), plant PSI-LHCI and Fd:FNR complex from cyanobacteria. FNR binding site location is proposed to be at the foot of the stromal ridge and above the inner LHCI belt. It is expected to form contacts with PsaE, PsaB, PsaF and at least one of the LHCI. In addition, a ~4.5-fold increased affinity between FNR and PSI-LHCI under crowded 1 M sucrose environment led us to conclude that in C. reinhardtii FNR also functions as a subunit of PSI-LHCI.


Assuntos
Arabidopsis/metabolismo , Chlamydomonas reinhardtii/enzimologia , Ferredoxina-NADP Redutase/metabolismo , Ferredoxinas/metabolismo , NADP/metabolismo , Fotossíntese , Complexo de Proteína do Fotossistema I/metabolismo , Cristalografia por Raios X , Cianobactérias/metabolismo , Transporte de Elétrons , Ferredoxina-NADP Redutase/química , Ferredoxinas/química , Luz , Complexos de Proteínas Captadores de Luz , NADP/química , Complexo de Proteína do Fotossistema I/química , Conformação Proteica
13.
Phytochemistry ; 166: 112059, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31280092

RESUMO

The cyanobacterial phylum is currently divided into five subsections (I-V), with the latter two containing no or false-branching (nostocalean) and true-branching (stigonematalean) cyanobacteria. Although morphological traits (such as cellular division and secondary branches) clearly separate both types of heterocytous cyanobacteria, molecular evidence indicates that stigonematalean cyanobacteria (Subsection V) do not form a monophyletic group but instead are interspersed and nested within the nostocalean cyanobacteria (Subsection IV). To further resolve the phylogeny of heterocytous cyanobacteria, we here analyzed the distribution of heterocyte glycolipids (HGs) in the true-branching cyanobacterium Stigonema ocellatum SAG 48.90 (type genus of Subsection V) and compared it with the HG inventory of other stigonematalean and nostocalean cyanobacteria. The most dominant HGs in S. ocellatum SAG 48.90 were 1-(O-hexose)-27-keto-3,25-octacosanediol (HG28 keto-diol) and 1-(O-hexose)-3,25,27-octacosanetriol (HG28 triol), which together constituted ca. 94% of all HGs. In addition, 1-(O-hexose)-3-keto-27-octacosanols (HG28 keto-ols), 1-(O-hexose)-3,27-octacosanediols (HG28 diols), 1-(O-hexose)-3-keto-27,29-triacontanediol (HG30 keto-diol) and 1-(O-hexose)-3,27,29-triacontanetriol (HG30 triol) occurred in minor abundances. Heterocyte glycolipids previously reported to be unique for stigonematalean cyanobacteria, i.e. 1-(O-hexose)-3,29,31-dotriacontanetriols (HG32 triols) and 1-(O-hexose)-3-keto-29,31-dotriacontanediols (HG32 keto-diols), were not detected in S. ocellatum SAG 48.90. Comparison of the HG distribution pattern with those of other heterocytous cyanobacteria indicated that S. ocellatum SAG 48.90 is most closely related to the nostocalean families Rivulariaceae and Scytonemataceae, which is complementary to reconstructed 16S rRNA gene sequence phylogenies. Our HG-based data thus provides evidence for the polyphyly of stigonematalean cyanobacteria, independent from molecular approaches, and points to the need for a critical re-evaluation of the current taxonomy of heterocytous cyanobacteria.


Assuntos
Cianobactérias/classificação , Cianobactérias/metabolismo , Glicolipídeos/metabolismo , Filogenia , Cianobactérias/genética , RNA Ribossômico 16S/genética
14.
Sci Total Environ ; 689: 789-796, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31280161

RESUMO

The sesquiterpene geosmin, mainly originating from cyanobacteria, is considered one of the problematic odor compounds responsible for unpleasant-tasting and -smelling water episodes in freshwater supplies. The biochemistry and genetics of geosmin synthesis in cyanobacteria is well-elucidated and the geosmin synthase gene (geo) has been cloned and characterized in recent years. However, understanding the diversity, origin, and evolution of geo has been hindered by the limited availability of geo sequences to date. On the basis of the cloned geo sequences from16 filamentous geosmin-producing cyanobacterial species, representing 11 genera in Nostocales and Oscillatoriales, the diversity and evolution of geo in cyanobacteria was systematically analyzed in this study. Homologous alignment revealed that geo is highly conserved among the examined cyanobacterial species, with DNA sequence identities >0.72. Phylogenetic reconstruction and codon bias analysis based on geo suggest that cyanobacterial geo form a monophyletic branch with a common origin and ancestor for cyanobacteria, actinomycetes, and myxobacteria. The global ratio of nonsynonymous/synonymous nucleotide substitutions (dN/dS) was 0.125, which is substantially <1 and indicates strong purifying selection in the evolution of cyanobacterial geo. To add to further interest, horizontal gene transfer of cyanobacterial geo in evolutionary history was confirmed by the discovery of an incongruent coevolutionary relationship between geo and housekeeping genes 16S rDNA and rpoC. The present study enhances the fundamental understanding of cyanobacterial geo in diversity and evolution, and sheds light on the development of molecular assays for detection and molecular ecology research of geosmin-producing cyanobacteria.


Assuntos
Proteínas de Bactérias/genética , Cianobactérias/genética , Evolução Molecular , Variação Genética , Naftóis/metabolismo , Proteínas de Bactérias/metabolismo , Cianobactérias/metabolismo , DNA Bacteriano/análise , Filogenia , Análise de Sequência de DNA , Especificidade da Espécie
15.
World J Microbiol Biotechnol ; 35(8): 116, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31332538

RESUMO

Exploration of renewable energy sources is an imperative task in order to replace fossil fuels and to diminish atmospheric pollution. Hydrogen is considered one of the most promising fuels for the future and implores further investigation to find eco-friendly ways toward viable production. Expansive processes like electrolysis and fossil fuels are currently being used to produce hydrogen. Biological hydrogen production (BHP) displays recyclable and economical traits, and is thus imperative for hydrogen economy. Three basic modes of BHP were investigated, including bio photolysis, photo fermentation and dark fermentation. Photosynthetic microorganisms could readily serve as powerhouses to successively produce this type of energy. Cyanobacteria, blue green algae (bio photolysis) and some purple non-sulfur bacteria (Photo fermentation) utilize solar energy and produce hydrogen during their metabolic processes. Ionic species, including hydrogen (H+) and electrons (e-) are combined into hydrogen gas (H2), with the use of special enzymes called hydrogenases in the case of bio photolysis, and nitrogenases catalyze the formation of hydrogen in the case of photo fermentation. Nevertheless, oxygen sensitivity of these enzymes is a drawback for bio photolysis and photo fermentation, whereas, the amount of hydrogen per unit substrate produced appears insufficient for dark fermentation. This review focuses on innovative advances in the bioprocess research, genetic engineering and bioprocess technologies such as microbial fuel cell technology, in developing bio hydrogen production.


Assuntos
Eletrólise , Hidrogênio/metabolismo , Fontes de Energia Bioelétrica , Reatores Biológicos/microbiologia , Cianobactérias/metabolismo , Fermentação , Hidrogenase/metabolismo , Oxigênio/metabolismo , Fotólise , Fotossíntese
16.
Biochim Biophys Acta Mol Cell Res ; 1866(10): 1608-1617, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31295502

RESUMO

Due to the low absorbance in the far-red (FR) and near-infrared (NIR) "optical window", NIR fluorescent proteins (FPs) are powerful tools for deep imaging. Here, we report three new, highly bright NIR FPs termed BDFP1.8, BDFP1.8:1.8 (tandem BDFP1.8) and BDFP1.9, which evolved from a previously reported FR FP, BDFP1.6: a derivative of ApcF2 from Chroococcidiopsis thermalis sp. PCC7203. ApcF2 binds phycocyanobilin (PCB) non-covalently, while BDFPs, the derivatives of ApcF2, can bind biliverdin (BV) covalently. We identified that dimeric BDFP1.8 and monomeric BDFP1.8:1.8 have a 2.4-and 4.4-fold higher effective brightness, respectively, than iRFP720, which has the highest effective brightness among the reported NIR FPs. Monomeric DBFP1.9 (17 kDa) has one of the smallest masses among highly bright FPs in the FR and NIR regions. Enhancing the affinity between the apo-proteins and the BV chromophore is an effective method to improve the effective brightness of biliprotein FPs. Moreover, BDFP1.8 and 1.9 exhibit higher stability to temperature, pH and light than iRFP720. Finally, the highly bright NIR BDFP1.8 together with FR BDFP1.6 could effectively biolabel cells in dual colors.


Assuntos
Proteínas de Bactérias/química , Biliverdina/química , Proteínas Luminescentes/química , Microscopia de Fluorescência/métodos , Animais , Proteínas de Bactérias/metabolismo , Cianobactérias/química , Cianobactérias/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Fluorescência , Células HEK293 , Células HeLa , Humanos , Raios Infravermelhos , Luz , Modelos Moleculares , Imagem Óptica/métodos , Ficobilinas , Ficocianina , Conformação Proteica
17.
Int J Mol Sci ; 20(11)2019 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-31181593

RESUMO

The slow but temperature-insensitive adenosine triphosphate (ATP) hydrolysis reaction in KaiC is considered as one of the factors determining the temperature-compensated period length of the cyanobacterial circadian clock system. Structural units responsible for this low but temperature-compensated ATPase have remained unclear. Although whole-KaiC scanning mutagenesis can be a promising experimental strategy, producing KaiC mutants and assaying those ATPase activities consume considerable time and effort. To overcome these bottlenecks for in vitro screening, we optimized protocols for expressing and purifying the KaiC mutants and then designed a high-performance liquid chromatography system equipped with a multi-channel high-precision temperature controller to assay the ATPase activity of multiple KaiC mutants simultaneously at different temperatures. Through the present protocol, the time required for one KaiC mutant is reduced by approximately 80% (six-fold throughput) relative to the conventional protocol with reasonable reproducibility. For validation purposes, we picked up three representatives from 86 alanine-scanning KaiC mutants preliminarily investigated thus far and characterized those clock functions in detail.


Assuntos
Proteínas de Bactérias/genética , Peptídeos e Proteínas de Sinalização do Ritmo Circadiano/genética , Cianobactérias/genética , Mutação , Adenosina Trifosfatases/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Peptídeos e Proteínas de Sinalização do Ritmo Circadiano/química , Peptídeos e Proteínas de Sinalização do Ritmo Circadiano/metabolismo , Cianobactérias/metabolismo , Técnicas Genéticas
18.
Int J Mol Sci ; 20(12)2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-31208089

RESUMO

Cyanobacteria have cyanobacteriochromes (CBCRs), which are photoreceptors that bind to a linear tetrapyrrole chromophore and sense UV-to-visible light. A recent study revealed that the dual-Cys CBCR AM1_1186g2 covalently attaches to phycocyanobilin and exhibits unique photoconversion between a Pr form (red-absorbing dark state, λmax = 641 nm) and Pb form (blue-absorbing photoproduct, λmax = 416 nm). This wavelength separation is larger than those of the other CBCRs, which is advantageous for optical tools. Nowadays, bioimaging and optogenetics technologies are powerful tools for biological research. In particular, the utilization of far-red and near-infrared light sources is required for noninvasive applications to mammals because of their high potential to penetrate into deep tissues. Biliverdin (BV) is an intrinsic chromophore and absorbs the longest wavelength among natural linear tetrapyrrole chromophores. Although the BV-binding photoreceptors are promising platforms for developing optical tools, AM1_1186g2 cannot efficiently attach BV. Herein, by rationally introducing several replacements, we developed a BV-binding AM1_1186g2 variant, KCAP_QV, that exhibited reversible photoconversion between a Pfr form (far-red-absorbing dark state, λmax = 691 nm) and Pb form (λmax = 398 nm). This wavelength separation reached 293 nm, which is the largest among the known phytochrome and CBCR photoreceptors. In conclusion, the KCAP_QV molecule developed in this study can offer an alternative platform for the development of unique optical tools.


Assuntos
Biliverdina/química , Luz , Fitocromo/química , Fitocromo/metabolismo , Engenharia de Proteínas , Sequência de Aminoácidos , Biliverdina/metabolismo , Cianobactérias/genética , Cianobactérias/metabolismo , Estrutura Molecular , Fotorreceptores Microbianos/genética , Fotorreceptores Microbianos/metabolismo , Fitocromo/genética , Estabilidade Proteica
19.
Appl Biochem Biotechnol ; 189(4): 1127-1140, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31168708

RESUMO

Cyanobacteria have immense prospective as a platform for renewable energy; however, a major barrier in achieving optimal productivity is the low lipid yield. Fremyella diplosiphon, a model cyanobacterium, is an ideal biofuel agent due to its desirable fatty acid methyl esters (FAMEs). To enhance lipid content, we overexpressed the sterol desaturase (SD) gene in F. diplosiphon B481 wild type by genetic transformation. This effort resulted in a transformant (B481-SD) with a 64-fold increase in the SD gene at the mRNA transcript level, with no loss in growth and pigmentation. The transformant was persistently grown for over 32 generations indicating long-term stability and vitality. We observed 27.3% and 23% increases in total lipid content and unsaturated FAMEs respectively in B481-SD transesterified lipids with methyl octadecadienoate as the most abundant unsaturated component. In addition, we detected an 81% increase in FAME composition in the transformant compared with the wild type. Theoretical physical and chemical properties confirmed a FAME profile with very high cetane number (65.972-67.494) and oxidative stability (50.493-18.66 h) in the engineered strain. Results of the study offer a promising approach to augment F. diplosiphon total lipid content and unsaturated FAMEs, thus paving the way to enhance biofuel capacity of the organism.


Assuntos
Biocombustíveis , Cianobactérias , Ácidos Graxos Insaturados , Engenharia Metabólica , Cianobactérias/genética , Cianobactérias/metabolismo , Ésteres/metabolismo , Ácidos Graxos Insaturados/biossíntese , Ácidos Graxos Insaturados/genética
20.
Biosens Bioelectron ; 140: 111354, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31154252

RESUMO

Microliter-scale photosynthetic microbial fuel cells (micro-PMFC) can be the most suitable power source for unattended environmental sensors because the technique can continuously generate electricity from microbial photosynthesis and respiration through day-night cycles, offering a clean and renewable power source with self-sustaining potential. However, the promise of this technology has not been translated into practical applications because of its relatively low performance. By creating an innovative supercapacitive micro-PMFC device with maximized bacterial photoelectrochemical activities in a well-controlled, tightly enclosed micro-chamber, this work established innovative strategies to revolutionize micro-PMFC performance to attain stable high power and current density (38 µW/cm2 and 120 µA/cm2) that then potentially provides a practical and sustainable power supply for the environmental sensing applications. The proposed technique is based on a 3-D double-functional bio-anode concurrently exhibiting bio-electrocatalytic energy harvesting and charge storing. It offers the high-energy harvesting functionality of micro-PMFCs with the high-power operation of an internal supercapacitor for charging and discharging. The performance of the supercapacitive micro-PMFC improved significantly through miniaturizing innovative device architectures and connecting multiple miniature devices in series.


Assuntos
Fontes de Energia Bioelétrica/microbiologia , Cianobactérias/metabolismo , Técnicas Biossensoriais/instrumentação , Capacitância Elétrica , Eletricidade , Eletrodos , Desenho de Equipamento , Fotossíntese
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